What Is a Semiconductor Diode?

Semiconductor substances are the building blocks of modern electronics and computing devices. A semiconductor diode is an electrical component that allows current to flow in one direction only.

When the p-type region is connected to the negative terminal and the n-type region to the positive terminal, the free electrons in the n-type material wander into the p-type region through random thermal migration (diffusion). Here they combine with holes and cancel each other out.

What is a Semiconductor Diode?

Semiconductor diodes are important building blocks of modern electronic gadgets. They can act as insulators and conductors depending on their application. They are highly adaptable and can be customised for specific requirements or special capabilities. This flexibility has helped them become vital components in contemporary electronics like mobile phones, computers and radios.

The semiconductor diode consists of a p-n junction with metallic contacts at both ends that allow an external voltage to be applied. It allows current to flow easily in one direction but severely restricts the current flowing in the opposite direction. This makes it an essential component in circuits that need to protect the circuit from alternating current (AC) or transform AC to DC.

When the semiconductor is left unpowered (zero bias), a potential barrier develops across a region known as the depletion layer. This barrier discourages the diffusion of more majority carriers (electrons) into the n-region from the p-region. This leaves the n-region with few free electrons and a large number of holes. These holes are called minority carriers.

When a positive bias is applied to the semiconductor, the depletion layer reduces. The majority carriers are pushed semiconductor diode into the n-region, leaving the p-region with few electrons and a large number of holes. The resulting current is known as a forward current. This is why the symbol for a diode includes an arrow pointing against the direction of conventional current flow.

Diode Characteristics

Diodes conduct current in one direction and block it in the other, which allows them to serve as a crucial component for countless electronic devices. This unidirectional flow of electricity is a critical safety feature, and it’s made possible by the unique properties of semiconductor materials.

A diode consists of two semiconductor regions that meet at the junction point (p-n). The p-type region contains positively charged electrons, and the n-type region has negatively-charged holes. The metallic contacts on the extreme ends of the diode make it easy to apply voltage to the device. The polarity of the applied voltage determines how the diode behaves.

When the diode is in forward bias, a narrow depletion region forms at the junction and keeps current from passing through. As the diode continues to gain voltage, the height of the barrier decreases and more electrons cross the junction.

If the diode is reverse-biased, electrons and holes are recombined at the p-n junction to create photons that emit light. This process is known as radiative recombination and is a fundamental property of the p-n junction that enables diodes to produce light.

Diode Applications

Diodes are essential components in contemporary electronic gadgets, acting as insulators and conductors. They’re also used to protect circuits against overvoltage, as voltage regulators, and in rectification processes.

The most basic semiconductor diode consists of two electrodes called the cathode and anode. When the cathode is hot, it emits electrons into the vacuum. The anode then picks up these electrons. The result is that current flows in one direction. A more advanced version of semiconductor diode manufacturer the diode combines a P-N junction with various doping concentrations to give it specific characteristics, such as low forward resistance and fast switching speeds.

When a positive voltage (forward bias) is applied across the p-n junction, it increases free electrons and holes within the depletion region around the junction. This decreases the width of the depletion layer, allowing current to flow. If the p-n junction is reverse biased, free electrons and holes are pulled away from the junction, widening the depletion region, preventing current from flowing.

Advances in semiconductor technology and the development of new materials like Silicon Carbide (SiC) and Gallium Nitride (GaN), have led to improved efficiency and power handling capability, extending their application to more demanding applications. The ability to withstand higher voltages and temperatures allows for faster switching and reduces power loss. This improves performance and increases reliability. In addition, it enables new applications like overvoltage protection and signal detection.

Diode Bias

A diode allows current to flow only in one direction, from the positive terminal (anode) to the negative terminal (cathode). This characteristic is a key factor in its usefulness in a variety of applications, including rectification, where it converts AC into DC, and in protection circuits, where it prevents reverse currents from damaging sensitive components. The bias caused by the pn junction is responsible for this behavior.

When a diode is not biased, the electron levels on the n and p sides of the pn junction cancel each other out so that there are no current carriers in the space around the junction. The width of this depletion region is small enough that a very weak electrical current can pass through it.

However, if you apply a positive voltage potential between the n and p sides of the diode, this gives free electrons the energy they need to overcome the barrier potential and pass through the junction. Once through, they combine with the holes being pushed by the external voltage potential to move into the p side of the pn junction.

This causes the width of the depletion region to decrease, allowing stronger currents to flow through the diode. The voltage required to achieve this state is called the forward bias. If the applied voltage is too great, the diode will experience a breakdown, which is typically destructive.